The present invention relates to shaped seamless woven tubular prostheses and methods of manufacture. In particular, the present invention relates to implantable endoluminal prostheses used in the vascular system.
Tubular woven fabrics have been used for soft-tissue implantable prostheses to replace or repair damaged or diseased lumens in the body. In particular, endoprostheses are used in the vascular system to prevent the blood from rupturing a weakened section of the vessel. Such endoluminal conduits are generally affixed in a specified location in the vessel by means of stents, hooks or other mechanisms which serve to secure the device in place. Endoluminal tubular devices or conduits can also be used in other lumens in the body, such as in the esophagus and colon areas.
Vascular grafts have been used successfully for many years to replace segments of the diseased vessel by open surgical methods. These techniques, however, required long and expensive procedures which have a high degree of risk associated with them due to the complexity of the surgical procedures. Presently, non-invasive techniques for treating body lumens, such as vessels in the vascular system, have become more prominent because they present less risk to the patient and are less complex than open surgery. Generally, a doctor will make an incision in the femoral artery and introduce an endoluminal device by means of a catheter delivery system to the precise location of the damaged or diseased vessel. The device will generally include a stent and graft combination which is deployed from the delivery system and affixed in place usually by use of a balloon catheter. The balloon catheter is used to expand the stents which are attached to and most often contained within the graft portion. Expansion of the stent serves to both anchor the graft and to maintain the graft and the body lumen in the open state. In some cases, self-expanding stents or the like are used. Stents made from shaped-memory materials, such as nitinol, are also employed whereby radial expansion or contraction of the stent is designed to occur at specified temperatures.
The use of tubular endoluminal prostheses, however, requires a high degree of precision in the diameter of the tube, such that its external diameter matches the internal diameter of the body lumen very closely, thereby conforming to the internal surface of the body lumen. The vessels or lumens in the body, however, often vary in diameter and shape from one length to another, in addition to sometimes defining a tortuous path therebetween. This is particularly true with the vessels in the vascular system. Thus, tubular endoprostheses which are generally straight in configuration cannot accurately conform to all portions of the lumen which have these variations present. Oftentimes, the prosthesis wall will require a bunching or gathering within the lumen of the vessel which presents a long-term potential for thrombosis and generally creates a more turbulent environment for blood flow.
More recently, in recognition of certain problems in implanting and delivering endoluminal prostheses, a thinly woven graft has been made which is designed to closely fit the inner lumen of vessels. Such a graft is described in co-assigned and co-pending U.S. Ser. No. 08/285,334 filed on Aug. 2, 1994, herein incorporated by reference. The thinness of this graft allows for it to be easily packed into a catheter delivery system and occupy less space within the lumen when deployed. However, these grafts have been made in straight lengths or bifurcated structures using traditional weaving techniques which have specific limitations as to the final shape of the product and, in the case of bifurcated or multi-diameter grafts, the transition from one diameter to another occurs at a single point in the weave, creating a sudden change in the weaving pattern of the fabric. Such sudden changes, as further discussed herein, are considered undesirable.
Weaving is commonly employed to fabricate various tubular shaped products. For example, implantable tubular prostheses which serve as conduits, such as vascular grafts, esophageal grafts and the like, are commonly manufactured using tubular weaving techniques, wherein the tubular product is woven as a flat tube. In such weaving processes, a variety of yarns are interwoven to create the tubular fabric. For example, a set of warp yarns is used which represents the width of the product being woven, and a fill yarn is woven between the warp yarns. The fill yarn is woven along the length of the warp yarns, with each successive pass of the fill yarn across the warp yarns for each side of the tube representing one machine pick. Thus, two machine picks represent one filling pick in a tubular woven structure, since weaving one fill yarn along the entire circumference of the tube, i.e., one filling pick, requires two picks of the weaving machine. As such, in a conventional woven product, the fill yarn is woven along the length of the warp yarns for a multiple number of machine picks, with the woven product produced defined in length by the number of filling picks of the fill yarn and defined in width by the number of warp yarns in which the fill yarn is woven therebetween. Such terminology and processes are common in the art of textile weaving.
Woven tubular prostheses such as vascular grafts, having tapered diameter sections or tailored shapes such as those shown in the inventive figures discussed herein, have heretofore not been made without requiring manual customization in the form of cutting, splicing and/or tailoring with sutures. Continuous flat-weaving techniques have not been able to make diameter changes in a gradual manner, having a tapered tubular section transitioning from one diameter to another diameter. Instead, diameter changes in the woven product occur instantaneously, creating a sudden split in the warp yarns. Such a sudden split, such as at the crotch section of a bifurcated endoluminal graft, leaves gaps or voids in the weave at the splitting point. Thus, conventional bifurcated woven grafts have required sewing of the crotch section in order to insure a fluid-tight character. Such sewing is labor intensive and is generally done manually, thereby introducing the potential for human error and reliance on the technique of the technician.
Furthermore, the prior art techniques of forming tubular shapes have required manual cutting and suturing of standard woven tubes to the desired size and shape. Continuous weaving of tubular grafts to produce seamless gradual diameter transitions in devices has not been previously known. For example, the change from a first diameter to a second diameter in a single lumen, straight graft, in a continuous weaving process was not attempted due to the aforementioned limitations. Instead, individual grafts of different diameters would be individually woven and sutured together to make a continuous tube. The diameter change required customized cutting to gradually transition from one diameter to another. For example, in the case where a bifurcated graft having a 24 mm aortic section and leg sections with different diameters, e.g. 12 mm and 10 mm, the surgeon would manually cut and tailor one of the legs of a bifurcated graft which was formed having two equal leg sections with the same diameters, and suture a seam along that leg to form a leg of the desired different diameter. This customization required cutting and suturing. Such customization relied heavily on the skill of the physician and resulted in little quality control in the final product. Additionally, such grafts could not always be made in advance for a particular patient, since the requirements for such customization may not be known until the doctor begins the surgery or procedure of introducing the device into the body. Additionally, as previously mentioned, the suture seams take up considerable amounts of space when packed into the delivery capsule or other catheter-like device designed to deploy the endoluminal prostheses.
There is currently no prior art means to satisfy the variation in requirements from patient to patient for proper fit of the endoprosthesis. Prior art continuously woven bifurcated grafts not only suffered from the gap created at the warp yarn split, but they existed only with iliac leg portions having equal diameters. If different diameter iliac leg portions were required, this would again be accomplished through customization. One leg would be manually cut-off and another independently formed leg having a different diameter would be sutured on in its place.
Complex shapes, such as tubular xe2x80x9cSxe2x80x9d shaped or frustoconical shaped woven sections were not even attempted due to the impractibility, intensive labor and subsequent cost. Such shaped tubes could not practically be woven using prior art techniques.
In addition to requiring manual sewing steps, sutures used in prior art customized grafts create seams which are to be avoided in endoluminal prostheses, particularly because of the space which they take up when tightly packed into a catheter delivery system. Furthermore, such seams contribute to irregularities in the surface of the graft and potential weakened areas which are obviously not desirable.
Due to the impracticalities of manufacturing tubular grafts and endoprostheses, straight and bifurcated tubular grafts often required customization by doctors using cutting and suturing for proper size and shape.
With the present invention, designs are now possible which heretofore have not been realized. Thus, the weaving of gradually shaped tubular grafts in a continuous process to create seamless and void-free conduits for implantation in the body has heretofore not been possible. The present invention provides a process of producing such grafts, as well as providing the weaving structure inherent in products formed therefrom.
The present invention relates to flat-woven implantable tubular prostheses, and in particular endoluminal grafts, which have been continuously woven to form seamless tubular products having gradual changes in diameter along their length, as well as various shaped tubular sections formed from gradual changes in the number of warp yarns engaged or disengaged with the fill yarns during the weaving process. Changes in diameter and/or shape are accomplished by gradually engaging and/or disengaging selected warp yarns with the fill yarns in the weave pattern. It has been discovered that such a gradual transition can be accomplished using electronic jacquard looms controlled by computer software. Such engaging and/or disengaging of warp yarns can change the diameter of the tube in a manner which creates a seamless and gradual transition from one diameter to another. Additionally, such engagement and/or disengagement can be used to create tubular vascular prostheses and the like which have any number of shapes as depicted and further described herein.
Thus, in one embodiment of the present invention there is provided, a flat-woven implantable tubular prosthesis having warp yarns and fill yarns including first and second spaced apart portions which define therebetween a transition tubular wall extent, the first portion having a first diameter and the second portion having at least a second diameter different from the first diameter. The tubular prosthesis further includes a weaving pattern along the transition tubular wall extent, said weaving pattern having a gradual change in the number of warp yarns to provide a seamless transition between the first and second portions.
In another embodiment of the present invention there is provided, a flat-woven implantable tubular prosthesis including first and second ends defining a tubular wall therebetween, with the tubular wall including warp yarns and fill yarns. The tubular wall is defined by a first elongate woven section with a first selected number of warp yarns therealong to define a first tubular internal diameter, and a second elongate woven section seamlessly contiguous with the first woven section and having a gradual change in the number of warp yarns therealong to define at least a second tubular internal diameter.
In an alternative embodiment of the present invention, there is provided, a flat-woven tubular implantable prosthesis having warp yarns and fill yarns including first and second ends defining a tubular wall therebetween, with the tubular wall having a first woven extent with a first selected number of warp yarns therealong to define a first tubular internal diameter, a transitional second woven extent contiguous with the first woven section with at least a second selected number of warp yarns therealong to define at least a second tubular internal diameter which is different from the first tubular internal diameter, and at least a third woven extent contiguous with the second woven extent with a third selected number of warp yarns which is different from the first and said second selected number of warp yarns, with the third woven extent defining a third tubular internal diameter which is different from the first and second tubular internal diameters.
Additionally, methods of forming such endoluminal prostheses are also provided. In one of such methods, there is provided a method of forming a seamless flat-woven implantable tubular prosthesis including the steps of weaving a tubular wall having transitional diameter along a longitudinal extent thereof, such weaving including gradually engaging or disengaging additional warp yarns along the extent to transition from a first diameter to a second diameter different from the first diameter.
Another embodiment of the methods of the present invention includes a method of making a seamless flat-woven implantable tubular prosthesis including weaving a first section of the prosthesis having a first diameter using a first selected number of warp yarns, and transitioning to a second section of the prosthesis having a second diameter different from the first diameter by gradually engaging or disengaging warp yarns.
Additionally included in the present invention is a method of forming a flat-woven synthetic tubular implantable prostheses having a precise pre-determined internal diameter (D) including the steps of: (i) choosing a desired weave pattern; (ii)providing a desired yarn and yarn size for the weaving pattern; (iii) providing a desired density (xcfx81) at which the yarn is to be woven; (iv) providing a number of warp yarns (S) required to weave a suitable tubing edge; (v) choosing a desired internal diameter (D) of the tubular prosthesis; (vi) calculating the total number of warp yarns (N) required to weave the tubular prosthesis having the internal diameter (D) using the formula:
N=S+(Dxc3x97xcfx81)
wherein N represents the total number of warp yarns required, S represents the number of warp yarns required to weave a suitable tubing edge, D represents the desired internal diameter and xcfx81 represents the number of warp yarns per unit of diameter.